The present invention relates to a clutch disc suitable for a friction clutch of an automobile.
Presently, light engines have been developed. However, the light engine generates large changes in torque which are transmitted through a clutch to driving mechanisms and may cause gear-attack noises in a transmission and a differential.
In order to solve the above problem, the applicant has already proposed a clutch disc in U.S. patent application Ser. No. 347,157 filed on Feb. 9, 1982, now U.S. Pat. No. 4,494,642. This clutch disc can sufficiently absorb the torque vibrations to reduce the noises in the gears.
In the clutch disc of the prior application, as shown in FIG. 1, a hub 1 has flange means 2 which is divided into an inner flange 3 formed integrally with the hub 1 and an outer flange 4. A pair of rather thin sub-plates 5 are fixed to both sides of the flange 4 and fitted to the outer periphery of the hub 1 to support the flange 4 with respect to the hub 1. Weak springs 6 for first torsion operation are disposed between the sub-plates 5 and the inner flange 3. Springs 7 for second and third operations are disposed between the outer flange 4 and the clutch and retaining plates 8 and 9.
In this disc, the clutch and retaining plates 8 and 9 torsionally turn or twist with respect to the flange 4 after the flange 4 turns through a predetermined angle with respect to the inner flange 3. Therefore, a maximum torsion angle can be sufficiently large. Since the springs 6 are soft with respect to the torsion of the flange, a rate of increase of torque with respect to increase of torsion angle is slow. Further, hysteresis torque changes in accordance with the change of the torsion angle. These features result in the advantage that the torque vibrations can be absorbed to reduce the noises in the gears.
However, in the clutch disc of large torsion angle and changeable hysteresis type, shown in FIG. 1, the flanges 3 and 4 are manufactured by forging, which increases costs. Further, it may be hard to position the flange 4 coaxially to the hub 1. Therefore, the springs 6 and 7 are also hard to be accurately positioned, and the sub-plates 5 may be broken. The pressures between the flange 3 and the sub-plates 5 are not stably fixed. Therefore, it is difficult to accurately generate an intended torque.
Accordingly, it is an object of the invention to provide an improved clutch disc, overcoming the above-noted disadvantages.
The essence of the invention is to provide hub flanges made of sheet metal and functioning also as conventional sub-plates.